Approximately 40 human chemokines have been described that function at least in part, by modulating a complex and overlapping set of biological activities important for the movement of lymphoid cells and extravasation and tissue infiltration of leukocytes in response to inciting agents (See, for example: P. Ponath, Exp. Opin. Invest. Drugs, 7:1-18, 1998). These chemotactic cytokines, or chemokines, constitute a family of proteins, approximately 8-10 kDa in size, that are released by a wide variety of cells, to attract macrophages, T cells, eosinophils, basophils, and neutrophils to sites of inflammation and also play a role in the maturation of cells of the immune system. Chemokines appear to share a common structural motif that consists of 4 conserved cysteines involved in maintaining tertiary structure. There are two major subfamilies of chemokines: the “CC” or β-chemokines and the “CXC” or α-chemokines, depending on whether the first two cysteines are separated by a single amino acid, i.e., CXC or are adjacent, i.e., CC.
These chemokines bind specifically to cell-surface receptors belonging to the family of G-protein-coupled seven-transmembrane proteins which are referred to as “chemokine receptors”, and mediate biological activity through these receptors. The chemokine receptor is classified based upon the chemokine that constitutes the receptor's natural ligand. Chemokine receptors of the β-chemokines are designated “CCR”; while those of the α-chemokines are designated “CXCR.” These chemokine receptors include but are not limited to CCR1, CCR2, CCR2A, CCR2B, CCR3, CCR4, CCR5, CCR6, CXCR3 and CXCR4 (see for a complete review, Murphy et al. Pharmacol. Rev. 52(1), 145-176 (2000)).
Chemokines are considered to be principal mediators in the initiation and maintenance of inflammation (see Chemokines in Disease published by Humana Press (1999), Edited by C. Herbert; Murdoch et al. Blood 95, 3032-3043 (2000)). More specifically, chemokines have been found to play an important role in the regulation of endothelial cell function, including proliferation, migration and differentiation during angiogenesis and re-endothelialization after injury (Gupta et al., J. Biolog. Chem., 7:4282-4287, 1998). Both chemokine receptors CXCR4 and CCR5 have been implicated in the etiology of infection by human immunodeficiency virus (HIV).
In most instances, HIV initially binds via its gp120 envelope protein to the CD4 receptor of the target cell. A conformational change appears to take place in the gp120 which results in its subsequent binding to a chemokine receptor, such as CCR5 (Wyatt et al., Science, 280:1884-1888 (1998)). HIV-1 isolates arising subsequently in the infection bind to the CXCR4 chemokine receptor. The observed binding of another related retrovirus, feline immunodeficiency virus, to a chemokine receptor without needing to bind first to the CD4 receptor, suggests that chemokine receptors may be the primordial obligate receptors for immunodeficiency retroviruses.
Following the initial binding by HIV to CD4, virus-cell fusion results, which is mediated by members of the chemokine receptor family, with different members serving as fusion cofactors for macrophage-tropic (M-tropic) and T cell line-tropic (T-tropic) isolates of HIV-1 (Carroll et al., Science, 276: 273-276 1997; Feng et al. Science 272, 872-877 (1996); Bleul et al. Nature 382, 829-833 (1996); Oberlin et al. Nature 382, 833-835 (1996); Cocchi et al. Science 270, 1811-1815 (1995); Dragic et al. Nature 381, 667-673 (1996); Deng et al. Nature 381, 661-666 (1996); Alkhatib et al. Science 272, 1955-1958, (1996)). During the course of infection within a patient, it appears that a majority of HIV particles shift from the M-tropic to the more aggressive pathogenic T-tropic viral phenotype (Miedema et al., Immune. Rev., 140:35 (1994); Blaak et al. Proc. Natl. Acad. Sci. 97, 1269-1274 (2000); Simmonds et al. J. Virol. 70, 8355-8360 (1996); Tersmette et al. J. Virol. 62, 2026-2032, (1988); Connor, R. I., Ho, D. D. J. Virol. 68, 4400-4408 (1994); Schuitemaker et al. J. Virol. 66, 1354-1360 (1992)). The M-tropic viral phenotype correlates with the virus' ability to enter the cell following binding of the CCR5 receptor, while the T-tropic viral phenotype correlates with viral entry into the cell following binding and membrane fusion with the CXCR4 receptor. Clinically, observations suggest that patients who possess genetic mutations in the CCR5 or CXCR4 appear resistant or less susceptible to HIV infection (Liu et al. Cell 86, 367-377 (1996); Samson et al. Nature 382, 722-725 (1996); Michael et al. Nature Med. 3, 338-340 (1997); Michael et al. J. Virol. 72, 6040-6047 (1998); Obrien et al. Lancet 349, 1219 (1997); Zhang et al. AIDS Res. Hum. Retroviruses 13, 1357-1366 (1997); Rana et al. J. Virol. 71, 3219-3227 (1997); Theodorou et al. Lancet 349, 1219-1220 (1997)).
Despite the number of chemokine receptors which have been reported to mediate HIV entry into cells, CCR5 and CXCR4 appear to be the only physiologically relevant coreceptors used by a wide variety of primary clinical HIV-1 strains (Zhang et al. J. Virol. 72, 9307-9312 (1998); Zhang et al. J. Virol. 73, 3443-3448 (1999); Simmonds et al. J. Virol. 72, 8453-8457 (1988)). Fusion and entry of T-tropic viruses that use CXCR4 are inhibited by the natural CXC-chemokine stromal cell-derived factor-1 (SDF-1). On the other hand, fusion and entry of M-tropic viruses that use CCR5 are inhibited by the natural CC-chemokines namely, Regulated on Activation Normal T-cell Expressed and Secreted (RANTES or CCL5) and Macrophage Inflammatory proteins (MIP-1 alpha and MIP-1 beta or CCL3 and CCL4, respectively). SDF-1 is known as CXCL12 or Pre B-cell stimulating factor (PBSF).
However, the binding of chemokine receptors to their natural ligands appears to serve a more evolutionary and central role than only as mediators of HIV infection. The binding of the natural ligand, PBSF/SDF-1 to the CXCR4 chemokine receptor provides an important signaling mechanism. CXCR4 or SDF-1 knock-out mice exhibit cerebellar, cardiac and gastrointestinal tract abnormalities and die in utero (Zou et al., Nature, 393:591-594 (1998); Tachibana et al., Nature, 393:591-594 (1998); Nagasawa et al. Nature 382, 635-638 (1996)). CXCR4-deficient mice also display hematopoietic defects (Nagasawa et al. Nature 382, 635-638 (1996)). Furthermore, the migration of CXCR4 expressing leukocytes and hematopoietic progenitors to SDF-1 appears to be important for maintaining B-cell lineage and localization of CD34+ progenitor cells in bone marrow (Bleul et al. J. Exp. Med. 187, 753-762 (1998); Viardot et al. Ann. Hematol. 77, 195-197 (1998); Auiti et al. J. Exp. Med. 185, 111-120 (1997); Peled et al. Science 283, 845-848 (1999); Qing et al. Immunity 10, 463-471 (1999); Lataillade et al. Blood 95, 756-768 (1999); Ishii et al. J. Immunol. 163, 3612-3620 (1999); Maekawa et al. Internal Medicine 39, 90-100 (2000); Fedyk et al. J. Leukocyte Biol. 66, 667-673 (1999); Peled et al. Blood 95, 3289-3296 (2000)).
The signal provided by SDF-1 on binding to CXCR4 may also play an important role in tumor cell proliferation and regulation of angiogenesis associated with tumor growth (See “Chemokines and Cancer” published by Humana Press (1999); Edited by B. J. Rollins; Arenburg et al. J. Leukocyte Biol. 62, 554-562 (1997); Moore et al. J. Invest. Med. 46, 113-120 (1998); Moore et al. Trends cardiovasc. Med. 8, 51-58 (1998); Seghal et al. J. Surg. Oncol. 69, 99-104 (1998)). Known angiogenic growth factors VEG-F and bFGF, up-regulated levels of CXCR4 in endothelial cells, and SDF-1 can induce neovascularization in vivo (Salcedo et al. Am. J. Pathol. 154, 1125-1135 (1999)). Furthermore, leukemia cells that express CXCR4 migrate and adhere to lymph nodes and bone marrow stromal cells that express SDF-1 (Burger et al. Blood 94, 3658-3667 (1999); Arai et al. Eur. J. Haematol. 64, 323-332 (2000); Bradstock et al. Leukemia 14, 882-888 (2000)).
The binding of SDF-1 to CXCR4 has also been implicated in the pathogenesis of atherosclerosis (Abi-Younes et al. Circ. Res. 86, 131-138 (2000)), renal allograft rejection (Eitner et al. Transplantation 66, 1551-1557 (1998)), asthma and allergic airway inflammation (Yssel et al. Clinical and Experimental Allergy 28, 104-109 (1998); J. Immunol. 164, 5935-5943 (2000); Gonzalo et al. J. Immunol. 165, 499-508 (2000)), Alzheimer's disease (Xia et al. J. Neurovirology 5, 32-41 (1999)) and arthritis (Nanki et al. J. Immunol. 164, 5010-5014 (2000)).
Platelets have also been shown to secrete the chemokine RANTES upon activation, and that the presence of RANTES on the endothelium promotes the arrest of monocytes on the inflamed endothelium, an important step in atherogenesis as the conversion of macrophages into foam cells in the subendothelium is a central process in atheroma formation (Tan, et al., Expert Opin. Investig. Drugs, 12(11):1765-1776 (2003)). Hence, the inhibition or prevention of the binding of RANTES, directly or indirectly, to the CCR5 receptor could potentially attenuate the development of atherosclerosis. For example, Met_RANTES has also been shown to inhibit the binding of monocytes to the activated endothelium (Tan, et al., supra).
In attempting to better understand the relationship between chemokines and their receptors, recent experiments to block the fusion, entry and replication of HIV via the CXCR4 chemokine receptor were carried out through the use of monoclonal antibodies or small molecules that appear to suggest a useful therapeutic strategy (Schols et al., J. Exp. Med. 186:1383-1388 (1997); Schols et al., Antiviral Research 35:147-156 (1997); Bridger et al. J. Med. Chem. 42, 3971-3981 (1999); Bridger et al. “Bicyclam Derivatives as HIV Inhibitors” in Advances in Antiviral Drug Design Volume 3, p 161-229; Published by JAI press (1999); Edited by E. De Clercq). Small molecules, such as bicyclams, appear to specifically bind to CXCR4 and not CCR5 (Donzella et al., Nature Medicine, 4:72-77 (1998)). These experiments demonstrated interference with HIV entry and membrane fusion into the target cell in vitro.
Bicyclams were also shown to inhibit fusion and replication of feline immunodeficiency virus (FIV) that uses CXCR4 for entry (Egberink et al. J. Virol. 73, 6346-6352 (1999)). CCR5 blocking agents include monoclonal antibodies, some which selectively block HIV coreceptor activity but not chemokine binding, and chemokine derivatives, such as truncated versions of RANTES, Met-RANTES, and AOP-RANTES and the viral chemokine KSHV vMIP-II, all which block both chemokine and HIV interaction with CCR5 but are not selective (reviewed by Murphy et al. Pharmacol. Rev. 52(1), 145-176 (2000)).
Additional experiments have shown that the bicyclam dose-dependently inhibits binding of 125I-labeled SDF-1 to CXCR4 and the signal transduction (indicated by an increase in intracellular calcium) in response to SDF-1. Thus, the bicyclam also functioned as an antagonist to the signal transduction resulting from the binding of stromal derived factor or SDF-1α, the natural chemokine to CXCR4. Bicyclams also inhibited HIV gp120 (envelope)-induced apoptosis in non-HIV infected cells (Blanco et al. Antimicrobial Agents and Chemother. 44, 51-56 (2000)).
Passive immunization with anti-MIP-1 alpha has been shown to delay the onset and reduce the severity of collagen-induced-arthritis (CIA) in mice, where the CIA model is an established murine model representing human rheumatoid arthritis (Szekanecz, Z., et al., AP, Seminars in Immunology, 15 (2003), p. 15-21). Other studies have also shown that agents that block the CCR5 receptor may provide a rational approach to the treatment of multiple sclerosis. Administration of anti-MIP-1 alpha antiserum has been shown to prevent CNS infiltration by PBMC in mice with experimental allergic encephalomyelitis, a rodent model of multiple sclerosis (Balashov, K. E., et al., Proc. Natl. Acad. Sci. USA, Vol. 96 (1999), p. 6873-6878).
Other studies involving chronic rejection of transplanted hearts or cardiac allograft vasculopathy (CAV) and acute renal allograft rejection have shown that blocking chemokine receptors such as CCR5 may provide unique therapeutic approaches in the treatment or prevention of such diseases (Yun J J, et al., Circulation, 2004, Vol. 109(7), p. 932-7, Panzer U., et al., Transplantation, 2004, Vol. 78(9), p. 1341-50). For example, antagonism of the chemokine receptors CCR1 and CCR5 with Met-RANTES attenuated CAV development by reducing mononuclear cell recruitment to the transplanted heart. Met-CCL5, an antagonist of CCR1 and CCR5, had been tested and shown to inhibit the growth of breast tumors (Robinson S C. et al, Cancer Res., 2003, Vol. 63(23), p. 8360-5).
Chemokines, as indicated above, play an important role and are implicated in a wide variety of human disease such as in autoimmune disease, allograft rejection, infection, allergies, neoplasia, and vascular abnormalities. In addition to its contributory role in HIV infection, the chemokine receptor CCR5 has been associated with diseases such as the inflammatory demyelinating diseases of the central nervous system, including multiple sclerosis and experimental autoimmune encephalomyelitis, rheumatoid arthritis, intestinal inflammation, allograft rejection, asthma, and cardiovascular disease (reviewed in Gerard et al. Natl. Immunol. 2(2), 108-115 (2001) and Luster, A., N. Eng. J. Med., 338 (7), 436-445 (1998)). The CCR5 receptor is expressed on T-lymphocytes, and macrophages and reports of CCR5 on neurons, astrocytes, capillary endothelial cells, epithelium, vascular smooth muscle, and fibroblast have been published. The natural ligands that bind to the CCR5 receptor, in addition to RANTES and MIP-1 alpha/beta, are monocyte chemoattractant protein 2 (MCP-2 or CCL8).
U.S. Pat. Nos. 5,583,131; 5,698,546; 5,817,807; 5,021,409; and 6,001,826 which are incorporated herein in their entirety by reference, disclose cyclic compounds that are active against HIV-1 and HIV-2 in in vitro tests. It was subsequently discovered and further disclosed in PCT WO 02/34745 that these compounds exhibit anti-HIV activity by binding to the chemokine receptor CXCR4 and/or CCR5 expressed on the surface of certain cells of the immune system. This competitive binding thereby protects these target cells from infection by HIV which utilize the CXCR4 receptor for entry. In addition, these compounds antagonize the binding, signaling and chemotactic effects of the natural ligand for CXCR4, the chemokine stromal cell-derived factor 1α (SDF-1). Furthermore, these compounds demonstrate protective effects against HIV infection of target cells by binding in vitro to the CCR5 receptor.
Additionally, U.S. Pat. No. 6,365,583 discloses that these cyclic polyamine antiviral agents described in the above-mentioned patents/patent applications have the effect of enhancing production of white blood cells as well as exhibiting antiviral properties. Thus, these agents are useful for controlling the side-effects of chemotherapy, enhancing the success of bone marrow transplantation, enhancing wound healing and burn treatment, as well as combating bacterial infections in leukemia.
PCT WO 00/56729, PCT WO 02/22600, PCT WO 02/22599, and PCT WO 02/34745 describe a series of heterocyclic compounds that exhibit anti-HIV activity by binding to the chemokine receptors CXCR4 and CCR5 expressed on the surface of certain cells of the immune system. This competitive binding thereby protects these target cells from infection by HIV which utilize the CXCR4 or CCR5 receptors for entry. In addition, these compounds antagonize the binding, signaling and chemotactic effects of the natural ligand for CXCR4, the chemokine stromal cell-derived factor 1α (SDF-1) and/or the natural ligand for CCR5, the chemokine RANTES.
The chemokine receptor, CXCR4 has been found to be associated with the vascularization of the gastrointestinal tract (Tachibana et al., Nature, 393:591-594 (1998)) as well as in hematopoiesis and cerebellar development (Zou et al., Nature, 393:591-594 (1998)). Interference with any of these important functions served by the binding of pre-B-cell growth-stimulating factor/stromal derived factor (PBSF/SDF-1) to the CXCR4 chemokine receptor results in lethal deficiencies in vascular development, hematopoiesis and cardiogenesis. Similarly, fetal cerebellar development appears to rely upon the effective functioning of CXCR4 in neuronal cell migration and patterning in the central nervous system. This G-protein-coupled chemokine receptor appears to play an important role in ensuring the necessary patterns of migration of granule cells in the cerebellar analogue.
Herein, we disclose compounds that have unique chemical attributes and that exhibit protective effects against HIV infection of target cells by binding to chemokine receptor CCR5. In addition, these compounds antagonize the binding, signaling and chemotactic effects of the natural ligand for CCR5, the chemokine RANTES.
Citation of the above documents is not intended as an admission that any of the foregoing is pertinent prior art. All statements as to the date or representation as to the contents of these documents is based on the information available to the applicants and does not constitute any admission as to the correctness of the dates or contents of these documents. Further, all documents referred to throughout this application are hereby incorporated in their entirety by reference herein.